We plan to study the environment of divalent metal ions responsible for activating enzymes. We will attempt to identify the nature of the metals' ligands, the liganding geometry and the effects of substrates, inhibitors and allosteric cofactors on the nature of the metal-protein interaction. We will then try to interpret these features in terms of the metal's catalytic role. A systematic study of enzymatically active metalloproteins substituted with a number of transition metal ions will be made. We will take advantage of the fact that contributions of metal d yields d electronic transitions to absorption, circular dichroism, magnetic circular dichroism and resonant raman spectra are very sensitive to the nature of the metal-enzyme interaction. Theoretical investigations will be made concerning the origin of these spectroscopic phenomena and their interpretation in terms of the metal's environment and chemical properties. We will also make kinetic studies, to determine the catalytic properties of the substituted metalloenzymes we will be using.